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System facilitates design, monitoring, validation of microwave-assisted multiphase aseptic processing.

Validating the continuous-flow microwave sterilization of low-acid multiphase foods requires the use of thermo-sensitive implants and simulated particles as carriers of these implants.

An appropriate system for inserting, monitoring and recovering such particles is needed in order to implement this technology under industrial processing conditions. The commercial availability of such a system for particle flow monitoring and validation under advanced microwave sterilization conditions could facilitate the faster penetration of these technologies into commercial use and help bring low-acid multiphase aseptic foods to market.

Scientists at North Carolina State University constructed and tested a system for inserting, monitoring and recovering such simulated particles that would be used as carriers of residence time and thermo-sensitive tags during the validation of low-acid aseptic multiphase foods. These foods would be sterilized using conventional or advanced microwave heating.

A semi-industrial 915 MHz 60 kW continuous-flow system consisting of a microwave heating unit, a hold tube, cooling unit and an aseptic bag filler was modified to include a port for inserting the simulated particles. The system also included expanded thermocouple probe ports, a dual concurrent system of giant magneto-resistive sensor arrays, signal amplifiers, data acquisition computers, and an in-line sieve for recovering the particles.

Half-inch cubic particles fabricated from rigid poly-methylpentene were assembled with cylindrical magnetic implants, bio-loads of B. stearothermophylus and B. subtilis spores, and enzymatic implants. The particles were passed through the system during microwave heating to 124 C.

Sensor arrays detected and recorded the passage of the particles containing individual cylindrical magnetic implants of 0.1 gram within stainless steel tubes of diameters ranging from 1.5 inches to 3 inches, with a flow rate of 1.5 gallons per minute. Expanded thermocouple ports enabled the passage of tagged particles through both the heating and hold tubes, however the particles were occasionally trapped within the cooling section.

Further information. K.P. Sandeep, Department of Food, Bioprocessing and Nutrition Sciences, Schaub Food Science Building 129, Box 7624, North Carolina State University, Raleigh, NC 27695; phone: 919-515-2957; fax: 919-515-7124; email:
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Publication:Microbial Update International
Date:Oct 1, 2009
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